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Ingredient Widely Used in Antibacterial Soap May Impair Muscle Function

Cleanliness may be next to godliness, but an ingredient widely used in antibacterial soaps is far from heaven-sent. A new study from the University of California Davis links triclosan with impaired activity in both heart and skeletal muscles. But although evidence for its toxicity is largely based on animal studies, the severity of the effects suggests a similar effect on human health at current levels of exposure. Chief among the concerns? Its potential contribution to heart disease and failure. “The effects of triclosan on cardiac function were really dramatic,” says Nipavan Chiamvimonvat, professor of cardiovascular medicine at UC Davis and a study co-author. “Although triclosan is not regulated as a drug, this compound acts like a potent cardiac depressant in our models.”

CHEMICAL ROMANCE

When scientists exposed individual fish and mouse muscle fibers to triclosan, they found that the chemical interfered with normal contraction. This was true when the animals were tested themselves: Mice showed up to a 25 percent reduction in heart function within 20 minutes of exposure to the chemical, as well as an 18 percent reduction in grip strength for up to an hour after exposure. Fish exposed to triclosan-laced water for seven days swam significantly slower than their undosed counterparts.

Although evidence for toxicity is largely based on animal studies, the severity of the effects suggests that triclosan could impact human health at current levels.

The findings, published in the August 13, 2012 issue of Proceedings of the National Academy of Sciences, floored even the scientists. “We were surprised by the large degree to which muscle activity was impaired in very different organisms and in both cardiac and skeletal muscle,” says Bruce Hammock, a professor in the UC Davis Department of Entomology and a study co-author. “You can imagine in animals that depend so totally on muscle activity that even a 10 percent reduction in ability can make a real difference in their survival.”

Triclosan was first introduced 40 years ago as a way to prevent bacterial infections in hospitals. Now found in facewash, deodorants, and other personal-care products, the germ-killing chemical has become a ubiquitous presence in our lives. But other than its use in some toothpastes to curb gingivitis, little evidence supports triclosan’s effectiveness over plain soap and water.

Experts also warn that overuse of the pesticide, which the U.S. Environmental Protection Agency classifies as a “possible carcinogen,” could result in the rise of drug-resistant superbacteria.

This isn’t the first time researchers have witnessed tricolsan’s potential harmful health effects. Previous studies linked the chemical to disrupted reproductive-hormone activity and diminished cell-signaling in the brain. Based on their results, the researchers call for greater restrictions by regulatory agencies.

“Triclosan can be useful in some instances, however it has become a ubiquitous ‘value added’ marketing factor that actually could be more harmful than helpful,” Hammock adds. “At the very least, our findings call for a dramatic reduction in its use.”